This invention relates generally to new compositions of matter and improved processes for the preparation thereof. More specifically, the present invention is directed to novel silylated hydroxyl squaraine compositions, novel deuterated hydroxyl squaraine derivatives, and to processes for preparing these compositions. The silylated products are primarily useful as colorants, and as intermediates for the preparation of hydroxyl squaraine derivatives, while the deuterated hydroxyl squaraine derivatives are useful as photoconductive compositions. Thus, for example the hydroxyl squaraines obtained from the silylated products of the present invention can be incorporated into layered photoresponsive imaging members, or devices, which members are responsive to visible light, and infrared illumination orginating in laser printing systems. The photoresponsive members envisioned can, for example, contain situated between a bottom photogenerating layer and a top hole transport layer, or situated between a top photogenerating layer and a bottom hole transporting layer and a supporting conductive substrate, a photoconductive composition, comprised of the squaraine compositions, especially the deuterated and nondeuterated hydroxyl squaraine derivatives prepared from the silylated products illustrated herein. Examples of other photoresponsive devices include those comprised of a conductive substrate, a hole transport layer, and as a top layer photoconductive hydroxyl squaraine derivatives; or wherein the photoconductive squaraine layer is situated between a conductive substrate and a hole transport layer. The photoconductive squaraine compositions are partially or totally responsible for enhancing the intrinsic properties of the photogenerating layer in the infrared and visible regions of the spectrum, thereby allowing the resulting imaging members to be sensitive to infrared and/or visible light.
Additional photoresponsive devices include those containing the photoconductive squaraine compositions in contact with a hole transport layer deposited on a supporting substrate with optional blocking and adhesive layers, and a protective top layer; or a similar device wherein the photoconductive layer is situated between the hole transport layer, and a supporting substrate. Other specific photoconductive devices included within the scope of the present invention are those comprised of a supporting substrate, an optional blocking layer, a photogenerating layer containing inorganic photoconductive materials, such as trigonal selenium, or organic photoconductive materials including phthalocyanines, a photoconductive layer comprised of the hydroxyl squaraine compositions, and a top hole transport layer. In a variation of the latter device, the hydroxyl squaraine photoconductive material can be located on the supporting substrate, or between the hole transport layer and the photogenerating layer. Several of these devices are illustrated in U.S. Pat. No. 4,415,639 entitled Layered Photoresponsive Devices, the disclosure of which is totally incorporated herein by reference.
Photoconductive imaging members containing certain squaraine compositions, particularly hydroxyl squaraines, are known, as described for example in U.S. Pat. Nos. 3,617,270 and 3,824,099. Further, there is described in a review article by Arthur H. Schmidt, SYNTHESIS, pages. 961-994, 1980 and the references therein, several methods for preparing squaric acid and squaraine derivatives including hydroxyl squaraines. Also known are layered photoresponsive devices with photogenerating layers and transport layers, reference U.S. Pat. No. 4,265,990. Examples of photogenerating layers disclosed in this patent include trigonal selenium, and phthalocyanine derivatives, while examples of transport layers that may be selected include certain aromatic amines and aromatic diamines dispersed in a resinous binder composition. Moreover, the use of specific squaraine pigments in photoresponsive imaging devices was disclosed in U.S. Pat. No. 4,415,639 entitled Layered Photoresponsive Devices wherein there is described an improved photoresponsive device containing a substrate, a hole blocking layer, an optional adhesive interface layer, an inorganic photogenerating layer, a photoconductive composition capable of enhancing the intrinsic properties of the photogenerating layer, and a hole transport layer. As photoconductive compositions for these devices, there can be selected various hydroxyl squaraine pigments. Additionally, there was disclosed in U.S. Pat. No. 3,824,099 certain photosensitive hydroxyl squaraine compositions. According to the disclosure of this patent, the squaraine compositions are photosensitive in normal electrophotographic imaging systems.
In a copending application, there are described novel squaraine compositions of matter, including bis-9-(8-hydroxyjulolidinyl)squaraine, and the use of these compositions in imaging members. One of the imaging members illustrated contains a supporting substrate, a hole blocking layer, an optional adhesive interface layer, an inorganic photogenerating layer, a julolidinyl photoconducting composition layer capable of enhancing the intrinsic properties of the photogenerating layer and a hole transport layer.
Processes for preparing squaraine compositions generally involve the reaction of squaric acid with an aromatic amine. Thus, for example, the julolidinyl squaraine compositions can be prepared by the reaction of an aromatic amine and squaric acid, in a molar ratio of from about 1.5:1 to 3:1 in the presence of a mixture of an aliphatic alcohol, and an optional azeotropic cosolvent. About 200 milliliters of alcohol to 0.1 mole of squaric acid are used, while from about 40 milliliters to about 4,000 milliliters of an azeotropic material, such as benzene, toluene, or the like are selected. The squaric acid coupling reaction is generally accomplished at a temperature of from about 50 degrees Centigrade to about 130 degrees Centigrade. Illustrative examples of aromatic amine reactants include 8-hydroxyjulolidine, 3-dimethylaminophenol 3-diethylaminophenol and the like while examples of aliphatic alcohols include 1-butanol, 1-pentanol and 1-octanol.
Additionally, there is described in another copending application the preparation of novel squaraine compositions, including for example, bis(4-N,N-dimethylamino-2-hydroxy-6-methylphenyl)squaraine by the reaction of squaric acid and 3-hydroxy-5-methyl-N,N-dimethylaniline(3-N,N-dimethylamino-5-methyl-phenol ). More specifically, as disclosed in this copending application the squaraine compositions involved are prepared by suspending squaric acid in an alcohol, followed by heating. Subsequently, there is then added to the resulting mixture an aromatic amine, such as 3-dialkylaminomethylphenol. This reaction is generally accomplished at a temperature of from about 50.degree. C. to about 130.degree. C. with stirring, wherein the desired product is isolated from the reaction mixture by known techniques and identified by analytical tools including NMR, mass spectroscopy and elemental analysis for carbon, hydrogen, oxygen and nitrogen.
While the above processes for preparing squaraine compositions may be suitable for their intended purposes, there continues to be a need for other processes wherein squaraine compositions, useful as photoconductive materials, can be prepared. Additionally, there remains a need for simple, economical processes for preparing squaraine compositions, wherein the squaraine products obtained are of higher purity, and smaller particle size than those obtained with many of the prior art processes. It is believed that the presence of impurities in the squaraine compositions causes the photosensitivity of these compositions to vary significantly, and in many instances, to be lower than the squaraine compositions prepared in accordance with the process of the present invention. Further, there continues to be a need for processes for the preparation of squaraine compositions, especially hydroxyl squaraines, of high purity, small pigment particle size, and improved morphological properties which, when selected for layered photoresponsive imaging devices, allow the generation of acceptable images, and wherein such devices can be repeatedly used in a large number of imaging cycles without deterioration thereof from the machine environment or surrounding conditions. Moreover, there remains a need for certain squaraine compositions, wherein the resulting products when incorporated into imaging members exhibit excellent pigment dispersion with uniform surface coverage, and superior sensitivity. Additionally, there is a need for processes for the preparation of photosensitive pigments containing novel deuterated hydroxyl squaraines. There also continues to be a need for processes of preparing hydroxyl squaraines, and novel deuterated hydroxyl squaraines, which possess high photosensitivity characteristics and desirable small particle sizes, enabling their use as photosensitive pigments with increased and consistent photosensitivity. Moreover, there remains a need for novel silylated products, which subsequent to hydrolysis are converted into deuterated and nondeuterated hydroxyl squaraine derivatives as indicated herein.